obtain SRA run IDs from BioSample IDs via

biosample2srr.md

1. Install Entrez Direct command line tool. See instructions here https://www.ncbi.nlm.nih.gov/books/NBK179288/
2. Make a list of BioSample IDs, one line per sample
3. Run the efetch, elink and xtract tools to fetch the SRA run IDs

cat biosample_ids.txt | while read SAMPLE ; do 
  SRR=`elink -db Biosample -id $SAMPLE -target sra \
    | efetch -format docsum \
    | xtract -pattern Runs -element Run@acc \
    | tr '\n' ','`
  echo $SAMPLE $SRR; 
  sleep 1;  
done  > sample2srr_map.txt